Muscle Fibers Essay

386 Words2 Pages
The muscle is made from bundles of muscle fibers. The muscle fibers are made up of bundles of myofibrils and the myofibrils are made from many sarcomeres that are positioned end-to-end. They have a striated look due to the light I-bands and dark A-bands. Type I Fibres These fibres, also called slow twitch or slow oxidative fibres, contain large amounts of myoglobin (location where oxygen is stored), many mitochondria and many blood capillaries therefore these fibers are red in color. This fiber type relies on aerobic metabolism. They split ATP at a slow rate and have a slow contraction velocity. These fibers have a high capacity to generate ATP by oxidative metabolic processes. Very resistant to fatigue (usually find an abundance of these type of fibers in runners) Aerobic Metabolism The metabolic process that occurs in the cells, by which the body uses oxygen to produce energy. Type II A Fibres These fibres, also called fast twitch or fast oxidative fibers, contain very large amounts of myoglobin, very many mitochondria and very many blood capillaries. Type II A fibers are also red, have a very high capacity for generating ATP by oxidative metabolic processes, split ATP at a very rapid rate, have a fast contraction velocity and are resistant to fatigue. Type II B Fibres These fibres, also called fast twitch or fast glycolytic fibres, contain a low content of myoglobin, relatively few mitochondria, relatively few blood capillaries and large amounts glycogen. These fibers appear white in color. Type II B geared to generate ATP by anaerobic metabolic processes so not able to supply skeletal muscle fibers continuously with sufficient ATP. Fatigue easily (More likely to accumulate lactic acid), split ATP at a fast rate and have a fast contraction velocity. Such fibres are found in large numbers in the muscles of the arms. The anaerobic energy pathway,
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